The ring-opening or metathesis polymerization of a wide variety of cyclic and polycyclic olefins is well known. Numerous patents and literature references, both U.S. and foreign, relate to the ring opening polymerization of olefins such as dicyclopentadiene in the presence of olefin metathesis catalyst systems. An illustrative catalyst system is disclosed by Sjardijn et al, U.S. Pat. No. 4,810,752, wherein substituted phenolic tungsten halides are employed in conjunction with triorganotin hydrides.
It is characteristic of many if not most ring-opening polymerizations that all carbon-carbon double bonds present in the ring or rings of the monomeric reactants are involved in the ring-opening polymerization. Thus, when one or more of the monomeric reactants contains multiple carbon-carbon double bonds the resulting polymer is a highly crosslinked thermoset polymer. These thermoset polymers exhibit a variety of useful properties but the nature of such properties is somewhat limited by the highly crosslinked character of the polymer.
In copending U.S. patent application Ser. No. 733,579 (T-2399), filed Jul. 22, 1991, there is described the preparation of Diels-Alder adducts of 4-vinylcyclohexene and cyclopentadiene. Among these adducts is a mono-adduct, i.e., 5-(3-cyclohexen-1-yl)2-norbornene. The ring-opening polymerization of this adduct is particularly useful because the polymer exhibits a varying degree of crosslinking, depending in part upon the polymerization environment. The resulting polymer, when not highly crosslinked, is useful in applications not available to thermoset polymers.
The 5-(3-cyclohexen-1-yl)-2-norbornene adduct, a 1:1 adduct of 4-vinylcyclohexane and cyclopentadiene, is produced together with other products by conventional Diels-Alder technology. However, the process selectivity to this particular adduct is lower than desired, e.g., 60% to 65%. The other reaction products include higher adducts of 4-vinylcyclohexene and cyclopentadiene, i.e., adducts with a higher proportion of cyclopentadiene, and cyclopentadiene oligomers. It would be of advantage to provide an improved process to increase the overall selectivity of the Diels-Alder process to the desired mono-adduct and decrease the overall production of heavier products.